Rosetta - a spacecraft in search of pristine matter
ASTRIUM NEWS RELEASE
Posted: June 23, 2001
In January 2003 the European spacecraft Rosetta is to set off in search of pristine matter. It will be launched on its long flight to the comet "Wirtanen" by the European launch vehicle Ariane 5. For approximately one year, it will orbit this tailed star at a distance of one kilometer and explore it in detail. At the same time, a probe will land on the comet's surface for surface-science investigations and analysis.
Rosetta Tacking through the Planetary System
The flight path itself already calls for new technical solutions. Even the thrust of the powerful Ariane 5 is not sufficient to directly inject the spacecraft on its way to the comet. The probe must rather gather momentum three times in the gravity fields of Mars and the Earth in order to get onto the right track. According to current planning this will take place in 2005 at Mars and the Earth and once again at the Earth in 2008. Only after the third swing-by maneuver will Rosetta be catapulted into the outer regions of the planetary system, where it will encounter comet Wirtanen.
In between these events, Rosetta will be largely on its own. This is the reason why the technically most complex workshare for industry is the so-called avionics pack which is also delivered by Astrium. It contains the software for the onboard computers and the attitude control system. Mind and body must operate faultlessly and to a large degree autonomously. The biggest single item under this contract, however, is instrument platform, which is also under the responsibility of Astrium.
The Asteroids Otawara and Siwa
During that time the surface will be imaged from a distance of approximately one kilometer. For the first time scientists, and of course the public, will be able to clearly see a cometary surface. Details down to one meter are expected to be discernible. The camera will be built by the Max-Planck Institute for Aeronomy in Katlenburg/Lindau, the experts that also developed the successful camera for Giotto.
Simultaneously, spectrometers will scan the surface in various spectral ranges down to the infrared range. This data will be used to determine the mineral and chemical composition of the surface material. The surface is expected to have the appearance of a dirty, crusted icy desert. Halley's Comet revealed long canyons, wide craters and up to 900-meter high hills. Nobody knows whether Wirtanen might look similar.
The German camera will also look for level terrain, since Rosetta will deploy a lander on the surface some time after having reached the comet.
Originally, two landers had been planned. One, called Champollion, was to be jointly built by France and the USA, the other one, Roland (Rosetta Lander), was planned as an exclusive German project. After the Americans' decision to withdraw from the project, Germany and France will jointly build one lander. This vehicle will land softly on the surface and will then have to be anchored. The reason for this is that the comet, measuring only a few kilometers, has an extremely low gravity. Its force of attraction is so low that a coin thrown in the air would disappear forever.
The lander will carry a series of complex instruments for the analysis of surface samples. Additionally, a camera will take panoramic pictures. The camera is a cooperative development between the Institute for Planetary Exploration of the German Aerospace Center (DLR) in Berlin and French scientists. It is even planned to lower a micro-camera into the bore-hole to determine the structure of the cometary crust.
While Rosetta orbits the comet, the latter will steadily approach the Sun. Wirtanen will wake up from the icy cold and start to heat up. Gases will evaporate from its surface and inside. They will drag along dust particles, and Wirtanen will thus form a coma and a tail. The 13 measuring instruments on board Rosetta will then begin the study of gas and dust. Approximately one year after Rosetta's encounter with the comet, Wirtanen will have reached the orbital point nearest the Sun, where it is most active. Shortly thereafter, the spacecraft mission will be completed. Wirtanen will then withdraw again into the outer and icy regions of the planetary system.
For the first time, scientists will thus have the opportunity to see "live" how a cometary surface evolves in the course of the "seasons". The pictures taken by Giotto already showed that, apparently, huge gas jets spout out of the crevasses in the surface. Rosetta will show this process in much more detail and thus help unravel further mysteries that surround the comets.
Comets - the Archives of Primeval Times
Comets, by comparison, are so small that no geological processes such as erosion or plate tectonics take place. There are presumably billions of cometary nuclei that slowly move around the Sun far outside Pluto's orbit. It is only when one of them ventures into the inner solar system that it will heat up so that gas will evaporate and it will appear as a tailed star in the sky.
Comets spend most of their "life" in the outer regions of the solar system where temperatures drop to nearly absolute zero. The cometary material is thus preserved in a deep-freeze state. Scientists therefore hope that Rosetta will help them determine the chemical composition of protosolar nebula in order to further explore the creation OT our solar system and thus of the Earth. In other words: Rosetta will be looking for the roots of our existence.
The Hubble Space Telescope's majestic view of the Eskimo Nebula. This spectacular poster is available now from the Astronomy Now Store.